. In 1932, H. J. Muller suggested a genetic test to determine whether a particular mutation whose phenotypiceffects are recessive to wild type is a null (amorphic)allele or is instead a hypomorphic allele of a gene.Muller’s test was to compare the phenotype of homozygotes for the recessive mutant alleles to the phenotype of a heterozygote in which one chromosomecarries the recessive mutation in question and thehomologous chromosome carries a deletion for aregion including the gene.In a study using Muller’s test, investigators examined two recessive, loss-of-function mutant alleles ofrugose named rg41 and rgγ3. The eye morphologiesdisplayed by flies of several genotypes are indicated inthe following table. Df(1)JC70 is a large deletion thatremoves rugose and several genes to either side of it.Genotype Eye surface Cone cells per ommatidiumwild type smooth 4rg41/rg41 mildly rough 2–3rg41/Df(1)JC70 moderately rough 1–2rg γ3/rg γ3 very rough 0–1rg γ3/Df(1)JC70 very rough 0–1a. Which allele (rg41 or rgγ3) is stronger (that is,which causes the more severe mutant phenotype)?b. Which allele directs the production of higher levelsof functional Rugose protein?
. In 1932, H. J. Muller suggested a genetic test to determine whether a particular mutation whose phenotypic
effects are recessive to wild type is a null (amorphic)
allele or is instead a hypomorphic allele of a gene.
Muller’s test was to compare the
carries the recessive mutation in question and the
homologous chromosome carries a deletion for a
region including the gene.
In a study using Muller’s test, investigators examined two recessive, loss-of-function mutant alleles of
rugose named rg41 and rgγ3
. The eye morphologies
displayed by flies of several genotypes are indicated in
the following table. Df(1)JC70 is a large deletion that
removes rugose and several genes to either side of it.
Genotype Eye surface Cone cells per ommatidium
wild type smooth 4
rg41/rg41 mildly rough 2–3
rg41/Df(1)JC70 moderately rough 1–2
rg γ3
/rg γ3 very rough 0–1
rg γ3
/Df(1)JC70 very rough 0–1
a. Which allele (rg41 or rgγ3
) is stronger (that is,
which causes the more severe mutant phenotype)?
b. Which allele directs the production of higher levels
of functional Rugose protein?
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